JPH02290239A - Fluidizing reaction device for magnetic micronized powder - Google Patents

Abstract

PURPOSE:To flow micronized powder uniformly by applying alternate current with different phases to a plurality of stages of electromagnets provided on the outside of the upper section of a reaction tube in a device feeding fluid from the bottom sectton of reaction tube and floating and flowing powder the powder in the tube. CONSTITUTION:Fluid (example: air) is fed from the bottom section of a reaction tube 1 to float and flow power (example: iron powder) in the tube 1. At that time, a plurality of stages of electromagnets 3 are provided on the outside of the upper section of reaction tube 1, and alternate current with different phases is applied to the electromagnets 3 in the respective stages. As a result, micronized powder of 10mu or less of grain diameter can be flowed uniformly, and the desired reaction can be carried out without sintering.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a reaction device capable of fluidizing ultrafine magnetic powder having a particle size of 10 μm or less.

[Prior art] Powder fluidization reactors generally fluidize the powder in the reaction tube by feeding fluid from the bottom of the reaction tube, and there is a dispersion device at the bottom of the reaction tube to support the powder. A plate is provided, and a cyclone, a filter, etc. for collecting the powder that flows out is provided above as necessary. The powder that can be fluidized by such a fluidization reactor has a particle size of 10 μm or more (
(edited by the Powder Technology Association, Powder Technology Handbook J, page 678, 1987). On the other hand, a technique is known that improves the fluidity of powder by applying vibration to a reaction tube to fluidize finer particles of powder.

(Problem to be solved by the invention) However, in the case of ultrafine powder with a particle size of 10 μm or less, increasing the flow rate of the fluid causes the powder to scatter and reduce the recovery yield, making it difficult to form a uniform fluidized bed. There was also the problem that the ultrafine powder would sinter because it was not possible to increase the flow rate of the fluid.On the other hand, the breakup plate has many small holes that allow the fluid to pass through. The small pores must be so small that they do not allow the powder to pass through.In the case of ultra-fine powder, the pore diameter must be extremely small, which creates a large fluid resistance and is difficult to put into practical use.For these reasons, the particle size A device for fluidizing ultrafine powder of 10 μM or less has not yet been developed.

[Means to solve the problem]

The present invention solves these problems and provides a reaction device for fluidizing ultrafine magnetic powder. Multiple stages of electromagnets are installed outside the top of the tube, and alternating current is applied to each stage of the electromagnet with a different phase.A vibration mechanism for the reaction tube is installed, and ultrafine magnetic powder is placed outside the bottom of the reaction tube. It is characterized by the provision of a magnet that prevents it from passing downward.

The reaction tube body is made of a material that is not affected by the magnetic field, such as glass, heat-resistant glass, quartz, alumina, and various ceramics. As the flow rate of the fluid in the reaction tube is increased, the fluid changes from an initial state to a fluidized region where the pressure drop is stable, as shown in FIG. 2, and then to a diffusion region and finally escapes to the outside of the system.

A magnetic fluidized bed is characterized by the presence of a diffusion region, which does not exist in conventional fluidized beds. In the reaction tube 1 of the present invention, the diameter of the lower part A is made small in order to prevent the falling of the powder and to accelerate the powder smoothly, so as to make it an outside-of-system blowout area.
It is preferable that the diameter of the pipe in the center part B is made into a diffusion region where the powder is fluidized in a diffused state, and the diameter of the upper part C is expanded to make it an initial state region in order to make it easier to decelerate, capture, and transport the powder downward. .

By using such a shape, the powder can be circulated and the reaction can be carried out uniformly.

Multiple stages of electromagnets are provided outside the upper part of the reaction tube to capture the powder and transport it downward. The number of electromagnets may be two or more stages, but preferably three or more stages, for example about 3 to 8 stages. The electromagnets in each stage are energized with alternating current with the phase changed sequentially. The strength of the magnetic field is adjusted depending on the type of ultrafine powder, the velocity of the fluid, etc., and is usually about 300 to 1000 Gauss.

A magnet is provided outside the lower part of the reaction tube to prevent the powder from passing downward. Although this magnet may be a permanent magnet, an electromagnet is preferable for operational reasons such as facilitating the upward movement of the powder after the fluid is delivered and for taking out the powder from below after the reaction is completed.

The applied current may be either alternating current or direct current. A plurality of electromagnets capable of transporting the powder both upward and downward can be further provided on the outside of the lower part of the reaction tube.

Switching between upward conveyance and downward conveyance of the powder can be performed by reversing the direction in which the phase of the alternating current changes. The upward conveyance allows the powder that has passed through the magnet section to be recovered, while the downward conveyance is useful for taking out the powder from the reaction tube after the reaction.

A vibration mechanism is provided in the reaction tube so that mechanical vibration can be applied. The vibration direction may be vertical, horizontal, radial, circumferential, or a combination thereof.

The fluid inlet side of the reaction tube is equipped with a fluid inlet means, a 2idft meter, etc., and the outlet side is equipped with a filter for collecting powder,
Cyclones etc. will be provided as appropriate.

The fluid may be an inert gas such as N2, Ar, He, or other reactive gas, or may be a liquid.

The method of fluidizing powder using the apparatus of the present invention will be explained with reference to FIG. 1. First, a current is applied to the electromagnet 2 at the bottom to form a magnetic field, and the powder is introduced into the reaction tube 1 from the top. do. When fluid is introduced from the lower end of the reaction tube and the current of the electromagnet 2 is decreased, the powder begins to rise inside the reaction tube.

When a current is applied to the multistage electromagnet 3 at the top of the reaction tube, the large diameter part C
The powder that has reached is swept c formed by the multi-stage electromagnet 3.
It is captured by the ff field and returned downward. In some cases, the electricity supply to the lower electromagnet 2 may be stopped as the fluid flow rate increases. Further, the multistage electromagnet 4 provided below the electromagnet 2 can be operated to transport the powder upward. When the desired flow state is obtained, a reaction gas is introduced to cause a reaction, and when the reaction is completed, the supply of fluid is stopped.

Then, the electromagnet 2 is de-energized and the powder is taken out downward. At this time, if necessary, the lower multi-stage electromagnet 4 is operated to transport the powder downward.

The device of the present invention contains iron powder, iron nitride powder, soft magnetic ferrite, permalloy, nickel, cobalt and compound powders thereof,
Silicon iron powder, amorphous alloy, acicular γ-Fe2U:
+ It fluidizes magnetic powder such as fine particles, and ultrafine powder with a particle size of IOμm or less, especially 3μm or less or l
It can also fluidize objects smaller than μm. The oscillating magnetic field fluidized bed formed in the reaction tube is effective for fluidizing reaction operations of fine powder having soft magnetic properties or powder containing fine powder. however,
The temperature is below the Curie point, and when a reaction is to occur, it is necessary that the desired reaction proceeds below the Curie point and at a rate that does not cause any operational problems.

Such an apparatus of the present invention is capable of synthesizing magnetic powder by solid state gas phase reaction, surface treatment, and CV of magnetic powder.
Surface coating modification in combination with D, combination with magnetic powder plasma. surface coating modification, mixing of magnetic particles, separation of magnetic and non-magnetic materials, separation of mixtures of powders with different Curie points, compositing of magnetic powders, ultrafine powder by CVD It is useful for use as a reaction vessel for magnetic materials, as a magnetic fluid synthesis device, as a magnetic fluid recovery device, and as a reaction vessel for ultrafine magnetic material by plasma CVD.

[Effect]

In the apparatus of the present invention, alternating current is applied to the upper electromagnets in multiple stages with different phases to form a magnetic field that sweeps the magnetic powder downward and prevents the powder from scattering outside the system. On the other hand, a magnet is provided at the bottom, and its magnetic field prevents the powder from falling.

In addition, by adding vibration to the reaction tube, a rocking force is applied to the magnetic powder captured in region C in Figure 1, and by using it complementary to the sweeping magnetic field, the downward transport effect can be enhanced. There is. It also acts as a sieve-off vibration to prevent powder from accumulating on the slope of the IBCfil area. Prevents fine powder from adhering to the reaction tube wall during operation. Furthermore, in taking out the powder after the reaction, it can be used as a vibration to prevent the powder from clogging the inside of the tube and to take it out smoothly. With these, the powder is completely uniformly dispersed and the contact between the solid particles and the reaction gas is enhanced. In addition, the powder is completely uniformly broken down to prevent sintering of the fine powder.

[Example] Example 1 A vibration device was further attached to the reaction tube l shown in FIG. 1, and an air pipe was connected to the lower end of the reaction tube. A flow meter and manometer were installed in the middle of the gas piping. A filter was attached to the top of the reaction tube.

The reaction tube is made of alumina and the diameter of part A is 201fl1Ilφ.
The diameter of part B is 301IIfflφ and the diameter of part C is 60m.
It was mφ. The upper multi-stage electromagnet 3 used had four stages, and the phase was shifted by 90 degrees to each stage so that alternating current could be applied. The multi-stage electromagnet at the bottom has three stages, and alternating current can be applied to each stage with the phase shifted by 120 degrees in the forward or reverse direction.

A current was applied to the electromagnet 2 and iron powder was introduced into the reaction tube.

The iron powder has a maximum particle size of 8 μm, an average particle size of 3 μm, and a density? ．． 8
6 X lo"kg/rrf was used. Air was introduced from the bottom of the reaction tube, and a current was applied to the multistage electromagnet 3.

As the iron powder rose, the current in magnet 2 was reduced. Vibration was applied to the reaction tube. The air flow velocity is 30 mm/
Fig. 3 shows the results of measuring changes in pressure loss after increasing the pressure to sec and then returning it back. On the other hand, for comparison, Fig. 4 shows the results of measuring changes in pressure drop in a conventional fluidized bed without applying a magnetic field or vibration. When vibration and magnetic field were not applied, the pressure drop fluctuated greatly in the early stage of fluidization, making it impossible to form a stable fluidized bed. On the other hand, by applying vibrations and a magnetic field, it was possible to form a stable fluidized bed, and the iron powder collected in the upper magnetic field fell down due to the vibrations and gravity, repeating the cycle. Further, the minimum fluidization speed was 5 mm/sec, which decreased to 173 when vibration and gravity were not applied.

Example 2 Using the apparatus used in Example 1, an iron nitride manufacturing apparatus shown in FIG. 8 was created. A circulation line is formed from the upper outlet 5 of the reaction tube 1, passing through the cyclone 6, the circulation pressure bomb 7, the flow meter 8, and the preheating section 9 in order, and connected to the lower port 10 of the reaction tube 1. In the middle of the circulation line, N is a carrier fluid.
2 gas cylinder 11, reactant gas N H :l gas cylinder 12 and H2 gas cylinder 13 are connected, and the valves to these cylinders are controlled by commands from a gas analyzer 14 which is also connected to the circulation line. It is opened and closed by Reaction tube 1
A heater 15 is disposed outside the center of the reaction tube 1, and a vibration transmission section 17 from a vibration generator 16 is connected to the lower part of the reaction tube 1. Directly below the reaction tube 1, a recovery section I8 is connected, branching off from the circulation line. On the other hand, an exhaust gas extraction line is connected to the circulation line near the upper outlet of the reaction tube I, and is connected to a leak valve 19, a cyclone 20, and an exhaust gas treatment equipment 2.
1 are connected in sequence.

Iron nitride was produced from the same iron powder used in Example 1 using such an apparatus. A current was applied to the electromagnet 2 to introduce iron powder into the reaction tube 1, and a current was applied to the multistage electromagnet 3.

N2 gas was flowed at a rate of 3 Ng/hr, vibration was applied to the reaction tube, and the current of the magnet 2 was decreased as the iron powder rose. After fluidization of iron powder reaches steady state, NH. Mixed gas of 50% gas and 50% H2 gas at approximately 1 m/sec
The center of the reaction tube was heated to 450°C with the heater 15.

N]43 gas and H2 gas were supplied to maintain the above concentration, and the gases were circulated for 10 minutes to cause a reaction. Thereafter, the temperature was increased to 200'C while adjusting the temperature to a gas partial pressure range at which iron nitride was stably generated.

Thereafter, the heating was stopped and the exhaust gas take-off line was opened.Meanwhile, the application of current to the electromagnet 2 was stopped and iron nitride powder was taken out from the lower part of the reaction tube.

The obtained iron nitride powder was pulverized for 5 minutes using a small vibrating mill, and the particle size was measured using a microtrack. The results are shown in FIG.

On the other hand, FIG. 6 shows the results of measuring the particle size of iron nitride powder obtained by adjusting the flow rate for fluidization in a conventional fluidized bed and reacting without applying vibration or magnetic field.

Next, the reaction was carried out in the same manner as above except that the gas circulation speed was changed, and the weight of the recovered iron nitride was measured to determine the amount of fine powder that flew out of the system. The results are shown as white circles in Figure 7. . On the other hand, the relationship between the circulation speed and the amount of fine powder that flew out of the system, which was determined by a similar reaction without applying vibration or magnetic field, is shown by a black square in the same figure.

〔Effect of the invention〕

The apparatus of the present invention can completely uniformly flow ultrafine powder of 10 μm or less, and can perform the desired reaction without sintering the fine powder.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing a state in which an apparatus according to an embodiment of the present invention is used. FIG. 2 is a diagram showing the relationship between the flow rate of fluid, the pressure, and the degree of fluidization. Figures 3 to 7 are diagrams showing the results of measurements with and without applying vibration and a magnetic field.
Figures 5 and 4 show the relationship between pressure drop and flow velocity, Figures 5 and 6 show the increase in particle size due to sintering, and Figure 7 shows the relationship between flow velocity and the amount of fine powder ejected from the system. . FIG. 8 is a diagram showing a flowchart of the apparatus used for the measurements in FIGS. 5 to 7. engraving of drawings

Claims (4)

[Claims] (1) In a device that feeds fluid from the bottom of a reaction tube to float and flow the powder inside the tube, multiple stages of electromagnets are installed outside the top of the reaction tube, and alternating current is applied to each stage of the electromagnets with different phases. Fluidization reaction device for ultrafine magnetic powder, characterized by: (2) The fluidization reaction device according to claim 1, which has a reaction tube vibration mechanism. (3) A device for causing powder in the tube to float and flow by feeding fluid from the lower part of the reaction tube, characterized in that a magnet is provided outside the lower part of the reaction tube to prevent the magnetic ultrafine powder from passing downward. Fluidization reaction device for magnetic ultrafine powder (4) The fluidization reaction device according to claim 1 or 2, further comprising a magnet provided at the lower part of the reaction tube to prevent the magnetic ultrafine powder from passing downward.